DESCRIPTION (provided by Candidate): Signaling peptides provide essential instructive cues for early vertebrate development. A small number of signaling pathways has been thought to be sufficient to explain most if not all aspects of early development. This idea has been challenged by our recent discovery that ende encodes a novel, highly conserved secreted peptide with essential functions during embryogenesis. Genome-wide technologies have allowed us to identify several other short secreted peptides that are expressed during embryogenesis. The goal of the proposed research is to identify the functions of these novel signaling peptides, using zebrafish as a model system. Aim 1 will investigate the roles of Ende in cell fate specification and cell migration during heart formation and identify its receptor. Aim 2 will investigate the in vivo functions of an additional 5 uncharacterized, secreted peptides during development. These studies have already led to the discovery of Ende as a novel essential signaling molecule during embryogenesis and will identify the roles of additional signaling molecules in early development. The proposed research has the potential to uncover novel signaling pathways and identify molecules with possible applications in tissue repair and in vitro differentiation.